Control system for radio beacons



Dec. 6, 1938. F. G. KEAR CONTROL SYSTEM FOR RADIO BEACON File July 29, 1936 lillll Patented Dec. 6, 1938 Washington Institute of Technology,

Inc.,

Washington, D. 0., a corporation of Delaware Application July 29, 1936, Serial No. 93,261

2 Claims.

This invention relates generally to the control of radio beacons of the type employing a plurality of intersecting characteristically modulated radiated fields, the area of intersection of which defines a zone in which the modulations impressed on the radiated carrier are of equal amplitude. This equi-signal zone, which may be identified by observing the respective amplitudes of the characteristic modulations over the area covered by the radiated fields, is directional in character and, being generally elongated and relatively narrow, may be employed as a directional guide or beacon for guiding mobile stations toward or away from the transmitting station. Continuous characteristic modulations may be impressed on the two carriers in the manner and for the result first disclosed by T. E. Brockstedt in Patent No. 1,865,826, which type of characteristic signal is preferable if a visual indication in the mobile station is desired.

It will be apparent, from a consideration of the method of establishing the beacon that the maintenance of a pre-determined directional characteristic thereof is dependent upon the maintenance of a pre-determined relationship between the two overlapping radiated fields. If both of the radiated fields change their positions in space, it will be apparent that the spatial position of the equi-signal Zone will be changed. Further, if one of the radiated fields changes its position in space with respect to the other radiated iield, the equi-signal zone will become either wider or narrower, depending upon the direction of the shift of the varying field. In either case the position of the real equi-signal zone will be changed and, if the equi-signal Zone had been previously aligned with a particular airport runway, will be moved from such alignment, thereby providing an incorrect path for the runway involved.

It has been found that the spatial and directional characteristics of the radiation from a given antenna are dependent upon and a function of the current owing in the antenna. Ac-

? cordingly, the spatial and directional characteristics of the equi-signal Zone defined by the overlapping radiations from a plurality of antennas will be varied by increase or decrease in the current in any one of the antennas. This effect is employed by the present invention as a means for monitoring and controlling the operation of a radio beacon transmitting means.

While the invention is intended to provide control means for directional radio beacons generally, it is o f particular use and adaptability when (Cl. Z50-11) such a beacon forms part of a radio landing system. It has heretofore been proposed and is known to employ a radio beacon of the type described as a guide for landing aircraft. In such a use of the beacon, the transmitter therefor is arranged on or adjacent to, either above or below, the surface of the ground, and is so placed with reference to a runway of the airport that the directional equi-signal Zone dened by the overlapping radiations therefrom is aligned with the runway. The pilot of an aircraft which is to be landed on the airport may, by proper interpretation of the instrument indications of the radiated fields of the beacon, guide the aircraft along or in line with the runway. Such a landing system preferably employs other co-operating means for bringing the craft to earth, such as the curved landing beam and the marker beacons, and such landing beams or marker beacons may be controlled within the broad scope of the invention.

It will be apparent that the runway beacon, providing as it does the sole directional guide for a landing aircraft in conditions of low or no visibility, must provide a correct path which is aligned with the properrunway in order to be of material assistance to a pilot attempting to land on an airport. It will be apparent that if the directional characteristic of the beacon is such that it will cause the aircraft to fly over or land along any other than a pre-determined path, the danger to persons carried by the landing aircraft may be very great.

It is, accordingly, an object of the present invention to provide means for controlling the operation of the runway localizing beacon of a radio landing system in such a manner that if the directional characteristics of the beacon Vary from pre-determined settings, the transmitting means establishing the beacon will be cie-energized. In a landing system provided with means according to the present invention, the runway localizing beacon will, whenever operating, conform to pre-determined directional and spatial characteristics and, if these are departed from, the beacon will be de-energized in order to prevent the establishment of an incorrect path in space.

In the absence of some means according to the present invention, the operator of the transmitting station will not be appraised of the fact that the directional beacon has shifted and is so disposed as to cause a landing aircraft to fly over an incorrect course or to land along a path which may not be cleared of obstructions. It is therefore of primary importance that a proper landing systern provide means for indicating to the operator of the transmitting station of the system the fact that the directional beacon is operating in a proper and pre-determined manner and is therefore in such a `position as to provide aproper path for a landing aircraft. Inasmuch as the operator of the ground station is constantly informed, by means according to the present invention, of the proper operation or de-energization of the runway localizer beacon, he may transmit such information to the pilot of a landing aircraft in order that the pilot may be fully apprised' of the condition of operation of the landing system.

It is therefore an .object of the invention to provide means at the transmitting station, or at any remote control station, for indicating by aural or visual means, the condition of e-:nergiran tion or de-energization of the transmitting means. station provided with the present invention will operate only when the'beacon established thereby adheres to pre-determined spatial and directional characteristics, it will be seen that an indication at the ground station or in the aircraft that the transmitting means is operating will Insure to the operator or observer that it is operating in a proper, predetermined manner.

Other objects and features of novelty of the invention will be made apparent by the following description and the appended drawing, it being expressly understood however that such description and drawing are merely illustrative of the invention, for the limits of which reference must be had to the appended claims.

Referring to the drawing, in which similar reference numerals refer-to like parts,

Fig. l is a circuit diagram disclosing the present invention, and

Fig. 2 is a circuit diagram disclosing a modified form of certain elements of the system illustrated in Fig. l.

The present invention provides means for controlling theoperation of a radio beacon, of the type known as the equi-signal beacon, in such a manner that if the beacon established departs from pre-determined spatial and directional characteristics the transmitters establishing the beacon will be de-energizedand this condition of de-energization will be made known to the operator of the ground station by aural or visual signals.

The equi-signal beacon which is controlled by the present invention,is dened by the intersecting or overlapping area of the directional radiations from two antenna systems I, 2, Vwhich may be loop antennas or any other directional type. Each of these antennas is supplied, by a transmitter 3, with characteristically modulated carrier. As stated hereinbefore the characteristic modulations are continuous signals of different audio frequencies. j

The transmitter 3 is supplied with electrical energy from main power supply lines it, 5 through leads e, l, in which is inserted the manually operable switch 8, whereby the transmitter may be disconnected from the source of power as desired. The leads 6, 'i also include, respectively the contacts 9, I@ of a relay II, each of which comprises a Xed contact member and a movalbe contact member. Both of the movable contact members are controlled by the relay in such a manner that during the normal condition of de-energization of tne relay the. switches 9, I will remain closed. As will be described more fully hereinafter the In view of the fact that a transmitting' relay II will be de-energized during proper cperation of the transmitter in' a predetermined manner, but will be energized to open the switches 9, lll and disconnect the transmitter 3 from the source of power when the directional characteristics of the beacon established by antennas I, 2 vary from pre-determined characteristics.

Means provided by the present invention for controlling the operation of the relay Il and thereby controlling the connection of the transmitter 3 to the source of power. Such means comprise-the coils I5, I6 which respectively receive the radiations from the transmitting antennas I, 2. The coils I5, I6 are preferably arranged locally with respect to the transmitting antennas I, 2 and are preferably inductively coupled thereto.

If desired, metallic plates may be substituted for the cols I5, I6 and may be capacitatively coupled to the transmitting antennas, or antennas arranged locally with respect to the transmitting antennas may be employed in place of the coils l5, i6, all without departing from the scope of the invention. l

The coil or antenna l5 may be arranged to receive principally the radiations from transmitting antenna l and is therefore preferably arranged substantially in the direction of maximum radiation from that antenna and in the direction of minimum radiation from antenna 2. Conversely, coil or antenna I 6 may be arranged substantially in the direction of maximum radiation from antenna 2 and in the direction of minimum radiation from antenna I.

Regardless of the spacing or coupling between coils l5, I6 and antennas I, 2, the currents induced in coils I5, I6 will be respectively proportional to the currents owing in antennas I, 2. As stated hereinbefore, the spatial and directional characeristics of the radiations from antennas i, 2 are functions of the current flowing in antennas I, 2 and of the amplitude of the carrier radiated by those antennas. The strength of the currents induced in coils I5, I6 will therefore lie between certainpre-determined limits so long as the currents in antennas l, 2 lie within predetermined limits and therefore so long as the radiations from antennas I, 2 adhere to pre-determined spatial and directional characteristics.

The received current in the coil I5, which is arranged to receive principally the radiations from antenna I consists of the radiated carrierl together with the characteristic modulation impressed thereon. 'I'he current in coil I6, which is so arranged to have induced therein principally the radiations from antenna 2, consists principally of the radiated carrier and the characteristic modulation radiated by antenna 2.

The current flowing in coil I5 due to the current flowing in antenna I is rectified by means of a rectifier, the oxide rectifier Il being preferably ernployed. The output of the rectifier I1 consists of a direct current component and an audio frequency current component, the latter being due to the modulation of the carrier in the source l, and this current is delivered to a second rectifier ifi, a condenser l! being inserted in the circuit leading to rectifier Il in order toremove the direct current component of the output of rectier Il. The audio frequency delivered to rectifier I8 is rectified thereby and the output of rectifier E8 is therefore a direct current which is proportional in strength to the amplitude of the current flowing in transmitting antenna I and the strength of which will therefore lie between pre-determined limits so long as the pre-determined directional characteristics of the radiations from antenna I are adhered to.

The current induced in coil I6 by the current iiowing in transmitting antenna 2 is rectied and ltered, in the same manner as described above, by means of rectiers 20 and 22 and condenser 2l. The otput of the second rectiiierv 20 will therefore be a direct current which will be proportional in value to the amplitude of the current owing in transmitting antenna 2 and the value of which will lie between pre-determined limits so long as the pre-determined directional characteristics of the radiation from antenna 2 are maintained.

The output terminals of rectiers i8 and 20 are respectively connected to coils 25, 26 which, respectively, form parts of relays denoted generally at 2l, 28. The relay 2l includes the two xed spaced contacts 29, 33 which are both connected to one terminal of the solenoid winding 3l of relay li by lead 32 and the movable contact 33 which is connected to main power supply line through lead 36 and the armature 35 of time delay relay 36. The relay 28, which is controlled by coil25,includes the Xed,spaced contact members 40, 4l, which are connected by lead 32 to the one terminal of winding 3| of relay il, the other terminal of which is connected by lead 50 to main power supply line at point 5l. Between the fixed contacts 50, I and movable into engagement with either is arranged the movable contact member i2 which is connected by lead 34 and armature 35 of time delay relay 36 to main power supply line 5.

The movable contact members 33, 32 are normally maintained out of engagement with xed contacts 3B, All, respectively, by action of the current in coils 25, 25 respectively. Means such as springs, are provided however, for moving the movable contacts into engagement with xed contacts 30, 4l when thev currents in either of coils 3B, 4l decreases below a pre-determined value.

The movable contact members 33, l2 are maintained out of engagement with the Xed Contact members 29, 4i), respectively, by some means, such as springs, but are adapted to be moved into engagement with such liXed contact members by the action of the current in the coils '25, 26 when such current increases above pre-determined limits, which will be sutlicient to overcome the force of the springs or other means tending to hold the iiXed and movable contact members apart.

It will be apparent from the above description that movement of either of the movable contact members 33 or l2 of the relays 25, 25 respectively, into engagement with any one of the fixed contact members 29, 35, 133, @l will cause winding 3l of relay ll to be connected across the main power supply lines il, 5 through lead 5G, winding 3l, lead 32, either of contacts 29, 3B, 43 or M, either of movable contacts 33, or 42, lead 35 and armature 35 of time delay relay 36, thereby energizing the relay Il and opening the switches 9, l to disconnect the transmitter 3 from the source ci power.

The winding of the time-delay relay 33 is connected directly across the main power supply lines d, 5 and such relay is accordingly supplied with electric energy as soon as the power supply lines are connected to a source of electric energy. It will be apparent that the transmitter 3 will be connected to the source of power immediately upon energization of the power supply lines 4, 5. On the contrary, the monitor system is not rendered operative until the time-delay relay closes, which will occur after a pre-determined interval following the connection of the main power supply lines to a source of electric energy. A switch 3l is provided in lead 34 which may be opened to disconnect the monitor system from other parts of the system.

Means are provided by the invention for indicating to the operator of the transmitting station, or at any remote control point, the condition of energization or de-energization of the transmitter 3. Such means comprise the signal 60 which may be of any aural or visual type, but which is preferably a green signal light, which is adapted to be energized when the transmitter 3 is energized and supplying energy to antennas I, 2. One terminal of the signal 5G is connected by lead 5| to main power supply line 5 at point 32, while the second terminal of the signal is connected to a Xed contact member 63. A second signal 6ft is provided which may also be of any desired aural or visual type, but which is preferably a red visual signal which is operated by operation of the monitor system to provide an indication that the transmitter 3 is deenergized or that the monitor system has not yet begun to function. One terminal of the signal 54 is connected to main power supply line 5 at terminal 32 through leadl, while the other terminal of the signal is connected to a iixed contact member 55 which is disposed adjacent to but spaced from the xed contact 63. Disposed between and movable into engagement with either of the Xed contacts 53, 65 is a movable contact member B'S which is connected to main power supply line 5 at terminal 5l through lead 5l. It will be apparent that if movable contact member 65 is moved into engagement with Xed contact 63 a circuit will be established from main power supply line 4 through lead 51, movable contact 66, fixed contact 63, green signal 60 and lead '6| to main power supply line 5, thereby energizing green signal 60 to indicate that the transmitter 3 is operating in a proper and pre-determined manner. If the movable contact G is moved into engagement with Xed contact member 55, a circuit will be established from main power supply line fl through lead 5l, movable contact 55, fixed contact 55, red signal til and lead ll to main power supply line 5, thereby energizing the red signal 54 to thereby indicate that the transmitter 3 is de-energized.

The contact members 63, 35 and 63 form a part of a relay denoted generally at lll. This relay is so constructed and adjusted that the movable contact member '86 thereof is normally in engagement with the fixed contact '55, thereby establishing a circuit through the red signal EG.

Means are provided by the invention for controlling the movement of the movable contact member 66 so that the same will move in a manner to provide an indication of the condition of operation of the transmitter 3. Such means comprises the winding or solenoid 'i3 which forms part of the relay 10 and which controls the movement of the movable contact member 66. One terminal of the solenoid 'H3 is connected to main power supply line 4 through lead "ll, switch 8, lead 6, switch 9 and lead 5, while the other terminal of the winding is connected to main power supply line 5 through lead 'l2 and armature 35 of time-delay relay 36. The relay 'it is so constructed and adjusted that when the solenoid I3 is energized, the movable contact member 66 will be moved into engagement with the fixed contact 63, thereby completing the circuit through the green signal t0 and energizing the same to indicate that the transmitter 3 is operating properly and that the monitor system is functioning. The circuit through solenoid 'I3 will be completed after operation of the time-delay relay 36 and after connection of the transmitter 3 to the source of power, and such circuit will be maintained closed so long as the switch 8 and the relay contacts 9 and IU are closed. When, however, for any cause, the switch 3 is manually opened, or the relay contacts 9, I0 are automatically opened by operation of either of relays 2l, 23, the circuit through winding I3 will be broken and the relay 'lil will be deenergized to thereby cause the movable contact member 66 to engage fixed contact 65 and thereby energize the red signal 64.

In the operation of the monitoring and signaling system described, the main power supply lines It, 5 may be connected to a source of power by means of a linestarter switch. The relay contacts 9, I El are normally closed and if the manual switch 3 is closed current will be supplied to transmitter E. The transmitter supplies to each of the antennas I, 2 characteristically modulated current at radio frequency, and the antennas each radiate the modulated carrier, the directional radiation elds of the two antennas being such as to overlap in space to provide an equi-signal zone which may be aligned as desired. The coils I5, I6, being locally arranged with respect to the antennas I, 2, will each respectively have induced therein currents corresponding to the radiations from one of the transmitting antennas. Current thereby induced in each of the coils is rectified and ltered to provide two direct currents, one in each of the coils or solenoids 25, 26 which operate the relays 2l, 28.

The directional characteristics and the spatial positions of the fields radiated by antennas I, 2, and consequently the position and directional characteristics of the equi-signal zone, are functions of the current flowing in antennas I, 2. The currents flowing in coils 25, 26 are proportional to the currents induced in coils I5, I5 and are also proportional to the currents owing in antennas I, 2 respectively. Accordingly, so long as the pre-determined directional characteristics and spatial disposition of the'fields radiated by antennas I, 2 are maintained, the currents iiowing in windings 25, 26 will remain within pre-determined limits.

The relays 2l, 28 are so adjusted and arranged that so long as the currents in coils 25, 2I5'remain within the pre-determined limits which dene the proper operation of the transmitting system, the movable contact members 33, l2 will remain out of engagement with the xed contact members 29, St, 46, 4I. When, however, the current in either coil decreases below a pre-determined value, denoting that the current in the corresponding one of the transmitting antennas has decreased and that the radiation therefrom has varied outside of pre-determined limits, the movable contact member of the affected relay will be moved by some means such as a spring, into engagement with the corresponding fixed contact member of the relay. If the current in either of coils 25, 26 increases above pre-determined limits, the movable contact member of the affected relay will be moved by the affected solenoid' into engagement with the corresponding fixed contact member of the relay.

Regardless of whether the movable contact member is operated by increase or decrease of current in coil 25 or 26, any movement of either movable Contact member into engagement with either of its associated xed contact members will cause a circuit to be completed through winding 3I of relay II, thereby energizing such relay and opening the relay contacts 9, Iii to disconnect the transmitter 3 from the source of power.

When the linestarter switch is closed to connect the main power supply lines to a source of power, the transmitter 3 will be immediately energized and, due to the fact that the movable contact B of the signal control relay 'I is normally in engagement with Xed contact 55, a circuit will be established through the red signal 64, thereby energizing this signal and indicating to the operator that the monitor system is not yet in operation. It will be seen that the circuit through winding 'I3 of relay 'It is open at this time due to the fact that the time-delay relay 38 has not yet closed.

The winding of the Vtime-delay relay 3S is connected directly across the main power supply lines and, accordingly, after a pre-determined interval following the connection of the main power supply lines to a source of power, the time-delay relay will close, thereby completing 'the circuit through winding '53 of signal control relay 'l and also connecting the movable contacts 33 and B2 of relays 2l, 28 to main power supply line 5. The monitoring system is now in condition to function and upon energization of lthe relay 'Ill by operation of the time-delay relay 36, the movable Contact member 66 of signal control relay I is moved into engagement With contact 63, thereby de-energizing the red signal 60 and energizing the green signal 6@ to indicate to the operator that the transmitter is energized and that the monitoring system is operating to properly control the operation of the transmitter.

So long as the transmitter 3 is operating properly and so long as the radiated fields maintain pre-determined spatial dispositions and directional characteristics the operation will be uninterrupted and the green signal 6G will remain energized. If the relay II is operated or if the manual switch 8 is opened, the transmitter 3 will be de-energized and the circuit through Winding i3 of relay l@ will be broken, thereby causing Vthe circuit through the green signal 60 to be broken and the red signal to be energized, indicating to the operator that the transmitter is deenergized. This information may be transmitted to an incoming aircraft by radiophone in order to provide the pilot thereof with proper information to enable him to land.

It will be seen that if the modulation is removed from the carrier in either of antennas I, 2 the corresponding relay 2 or 28 of Fig. l or 80 or BI of Fig. 2 will be operated thereby de-energizing the transmitter. This effect will be due to the presence of the condensers I9, 2i in the output circuits of the rectifiers I'! and 22, respectively, which eliminate the direct current output of the rectifiers El, 22 due to the unmodulated carrier.

In Fig. 2 of the drawing lthere is disclosed a modified arrangement of certain features of the invention. In this modification there is disclosed a different form of relay means, which modified form may be employed in place of either of the relays 2l, 28 of Fig. l. In Fig. 2 there are disclosed the relays 80, 8|, the coils 82, 83 of which are connected to the output terminals of a rectier which corresponds in function to the rectier I8 of Fig. 1. The winding 82 is adapted to control the movable contact member 84 which is normally held out of engagement with a fixed contact 85 by the action of current in coil 82, but which is adapted to be moved into engagement with the fixed contact member by some means, such as a spring, upon decrease off the current in coil 82 below a pre-determined limit. The second coil B3 of the relay 80 controls the operation of a second movable contact member 8l which is normally held out of engagement with xed contact member 8B by some means, such as a spring, and which is adapted to be moved into engagement with the fixed contact member by increase of the current in coil 83 above a predetermined limit.

While I have illustrated and described certain embodiments of my invention, it will be apparent to those skilled in the art that numerous variations, embodiments and improvements may be made therein without departing in any way from the scope of the invention, for the limits of which reference must be had to the appended claims.

I claim:

1. A control means for a radio transmitting system which comprises transmitting means adapted to establish a plurality of radiated iields, a source of power and means operable to connect said transmitting means to a source of power, said control means comprising a plurality of energy collecting means each of which is disposed within one of said fields, means for producing from each received radiation a current which is proportional in strength at all times to the strength of the radiation producing it, and separate means each continuously controlled by one of said produced currents and operable thereby to maintain the connection between the transmitting means and the source of power and operable in response to increase or decrease of the controlling produced current from predetermined upper and lower limits to cause the operation of said connecting means to disconnect the transmitting means from the source of power.

2. A radio system comprising transmitting means adapted to establish a plurality of radiated fields, a source of power, means operable to connect said transmitting means to said source of power, a plurality of energy receiving means each of which is positioned in one of said radiated elds and adapted to receive the radiations establishing such iield, means for producing from each received radiation a direct current which is proportional in strength at all times to the strength of the radiated eld from which it is produced, and separate control means each continuously controlled by one of said produced direct currents and operable thereby to maintain the connection between the transmitting means and the source of power and operable in response to any increase or decrease of the controlling current from predetermined upper and lower limits to cause the operation of said connecting means to disconnect the transmitting means from the source of power.

FRANK G. KEAR. 

